The present application is based on and claims under 35 U.S.C. xc2xa7 119 with respect to Japanese Patent Application Nos. 2000-292359 filed on Sep. 26, 2000, the entire contents of which are incorporated herein by reference.
The present invention relates to an oil pump apparatus, and more particularly, an oil pump apparatus driven by a drive source for supplying a predetermined amount of pressurized hydraulic oil to the hydraulic oil receiving portion by a control valve which can flow back a part of hydraulic oil discharged from the oil pump.
In Unexamined Published Japanese Patent Applications (Kokai) No.Hei.10 (1998)-73084, for example, there is disclosed a conventional oil pump apparatus. The conventional oil pump apparatus comprises an oil pump housing including a first suction port, a second suction port and a discharge port in the circumferential direction thereof, and a drive rotor and a driven rotor disposed rotatably eccentrically each other in the oil pump housing and forming a plurality of pump chambers in the circumferential direction of the rotor. When the drive rotor is driven by the drive source, each of the pump chambers is moved and is communicated to the first suction port, the second suction port and the discharge port in order, respectively.
In the above prior pump apparatus, a shape of the end portion of the second suction port adjacent to the first suction port is formed so as to be along the shape of the end portion of the pump chamber which abuts on the second suction port and which is sealed momentarily between the first suction port and the second suction port. Further, a shape of the end portion of the first suction port adjacent to the second suction port is formed so as to be along the shape of the end portion of the pocket which abuts the second suction port and which is sealed momentarily between the first suction port and second suction port. Thus, an efficient passage is obtained just before each of the pump chambers is sealed and just after the sealing condition of each of the pump chambers is opened.
Here, in a case where the construction of the above described prior oil pump apparatus is adapted to an oil pump apparatus 20 which has drive rotor 22 having four outer teeth 22a and driven rotor 23 having five inner teeth 23a disposed eccentrically in the oil pump housing 21 as shown in FIG. 1 and pump chambers R being able to change their volume are formed between the drive rotor 22 and the driven rotor 23, as shown by two dotted lines, the shape B1 of the end portion of the second suction port B adjacent to the first suction port A is formed so as to be along the shape R (s portion with slash) of the end portion of the pump chamber R which abuts on the second suction port and which is sealed momentarily between the first suction port A and the second suction port B. Further, as shown by one dotted line in FIG. 1, the shape Ao of the end portion of the first suction port A adjacent to the second suction port is formed so as to be along the shape (curving shape with projection toward inner circumference) R2 of the end portion of the pump chamber R which is adjacent to the first suction port and which is sealed momentarily.
In the above described construction, while the drive rotor 22 and driven rotor 23 are rotated by crank shaft 10 of the vehicle engine (internal combustion engine) counter-clockwise as shown in FIG. 1, when the pump chamber R is rotated to the location shown FIG. 2, the end portion of the pump chamber R on the rotational direction side is communicated to the second suction port B and the end portion shown by one dotted line of the pump chamber R on the anti-rotational direction side overlaps with the inner circumference portion of the first suction port A and is communicated to the second suction port A. Accordingly, while the first suction port A is communicated to the discharge port C with the operation of the control valve 30 by which the oil pump apparatus can flow a part of the hydraulic oil discharged from oil pump 20 to the suction side (while a spool 31 disposed in the control valve 30 slides against the biasing force of a spring 33 and closes the connection between a port 31c and a port 31d), the first suction port A and the second suction port B repeat connection and disconnection. The high pressure hydraulic oil flowed from the discharge port C to the first suction port A through the control valve 30 flows from the first suction port A to the second suction port B through the pump chamber R intermittently. Thus, the amount of the hydraulic oil supplied to the hydraulic oil receiving portion decreases. Further, the pulsation of the hydraulic pressure increases and the noise is generated.
The present invention provides an oil pump apparatus without the foregoing drawbacks.
In accordance with a first aspect of the present invention, an oil pump apparatus comprises an oil pump housing including a first suction port, a second suction port and a discharge port in the circumferential direction thereof, a drive rotor and a driven rotor disposed rotatably eccentrically in oil pump housing and forming a plurality of pump chambers in the circumferential direction of a rotor, and each of the pump chambers communicating to the first suction port, the second port and the discharge port in order, respectively, when the drive rotor and the driven rotor are rotated, wherein a shape of the end portion on the side of the anti-rotational direction at the second suction port is formed so as to be along a shape of the end portion on the side of the rotational direction at the pump chamber. The pump chamber is sealed momentarily between the first suction port and the second suction port, and a shape of the inner circumferential end portion of the first suction port is formed so as to be along the rotational trace of the end portion on the side of the anti-rotational direction at the pump chamber. The pump chamber is sealed momentarily between the first suction port and the second suction port, wherein a plural first pockets or penetrating holes which can be communicated to the first suction port at outer circumferential portion thereof and which cannot be communicated to each port at the same time are formed on the driven rotor, and a second pocket which can be closed at the inner circumferential portion of the pump housing located at the inner side with respect to the first suction port by the drive rotor which can be communicated respectively to the each pump chamber and the inner circumferential portion of the first pocket or penetrating hole is formed on the pump housing and can communicate each pump chamber with the first suction port through the first pocket or penetrating hole when each pump chamber is communicated to the first suction port.
In accordance with the second aspect of the present invention, an oil pump apparatus comprises an oil pump housing including a suction port, a first discharge port and a second discharge port in the circumferential direction thereof, a drive rotor and a driven rotor disposed rotatably eccentrically in a oil pump housing forming a plurality of pump chambers in the circumferential direction of a rotor. Each of the pump chambers communicates to the suction port, the first discharge port and the second discharge port in order, respectively, when the drive rotor and the driven rotor are rotated, wherein a shape of the end portion on the side of the rotational direction at the first discharge port is formed so as to be along a shape of the end portion on the side of the anti-rotational direction at the pump chamber. The pump chamber is sealed momentarily between the first discharge port and the second discharge port, and a shape of the inner circumferential end portion of the second discharge port is formed along the rotational trace of the end portion in the rotational direction at the pump chamber. A plural first pockets or penetrating holes which can be communicated to the second discharge port at outer circumferential portion thereof and which can not be communicated to each port at the same time are formed on the driven rotor. A second pocket which can be closed at inner circumferential portion of the pump housing located at inner side with respect to the second discharge port by the drive rotor which can be communicated respectively to the each pump chamber and the inner circumferential portion of the first pocket or penetrating hole is formed on the pump housing. Through the first pocket or penetrating hole, each pump chamber communicates with the second discharge port.
In the first aspect of the oil pump apparatus, the pump chamber sealed momentarily is rotated toward that location and communicates with the second suction port, the end portion of the pump chamber on the side of the rotational direction is communicated to the second suction port. However, the end portion of the pump chamber on the side of the anti-rotational direction does not overlap with the first suction port and is not communicated to the discharge port with the operation of the control valve, the first suction port is not communicated to the second suction port through the pump chamber. Therefore, the high pressure hydraulic oil flowed from the discharge port to the first suction port through the control valve does not flow from the first suction port to the second suction port through the pump chamber, and the amount of the hydraulic oil supplied to the hydraulic oil receiving portion is prevented from decreasing. Further, the pulsation of the hydraulic pressure decreases and the generation of the noise is prevented.
Further, just before the pump chamber is sealed momentarily, the hydraulic oil is sucked from the first suction port to the pump chamber through the end portion of the first suction port on the side of the rotational direction and a portion of the pump chamber that overlaps with the end portion of the first suction port in the rotational direction, and the hydraulic oil is sucked from the first suction port to the pump chamber through the first pocket or penetrating hole formed on the driven rotor and the second pocket formed on the drive rotor. Therefore, the area of the communicating passage between the first suction port and the pump chamber can be increased and the flow resistance can be decreased. As a result, the cavitation can be prevented and the pulsation is decreased.
On the other hand, in accordance with the second aspect of the oil pump apparatus, when the pump chamber communicated to the first discharge port is rotated toward the location where the pump chamber is sealed momentarily, the end portion of the pump chamber on the rotational direction does not overlap with the second discharge port and is not communicated to the second discharge port. Accordingly, while the first discharge port is communicated to the suction port with the actuation of the control valve, the first discharge port is not communicated to the second discharge port through the pump chamber and the high pressure hydraulic oil does not flow. Therefore, the amount of the hydraulic oil supplied to the hydraulic pressure is prevented from decreasing and the generation of the noise is also prevented.
Further, just after the pump chamber is sealed momentarily, the hydraulic oil is discharged from the pump chamber to the second discharge port through the end portion of the second discharge port on the side of the anti-rotational direction and a portion of the pump chamber that overlaps with the end portion of the second discharge port on the side of the anti-rotational direction. Also, the hydraulic oil is discharged from the pump chamber to the second discharge port through the first pocket or penetrating hole formed on the driven rotor and the second pocket formed on the pump housing. Therefore, the area of the communicating passage between the pump chamber and the second discharge port can be increased and the flow resistance can be decreased. As a result, the pumping loss as well as the pulsation is decreased.